K.V.AFS WADSAR CLASS (XII) CHEMISTRY

from the compound formed when n-butyl bromide is reacted with sodium. Give the structural formula of (a) and write the equations for all the reactions...

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K.V.AFS WADSAR CLASS (XII) CHEMISTRY SURE SHOT QUESTIONS: 1) Distinguish between (i) Hexagonal and monoclinic unit cells (ii) Face-centred and end-centred unit cells. 2) Atoms of element B form hcp lattice and those of the element A occupy 2/3rd of tetrahedral voids. What is the formula of the compound formed by the elements A and B? 3) An element has a body-centred cubic (bcc) structure with a cell edge of 288 pm. The density of the element is 7.2 g/cm3. How many atoms are present in 208 g of the element? 4) Calculate (a) molality (b) molarity and (c) mole fraction of KI if the density of 20% (mass/mass) aqueous KI is 1.202 g mL-1. 5) If N2 gas is bubbled through water at 293 K, how many millimoles of N2 gas would dissolve in 1 litre of water. Assume that N2 exerts a partial pressure of 0.987 bar. Given that Henry’s law constant for N2 at 293 K is 76.48 kbar. 6) State Henry’s law and solubility. 7) 2 g of benzoic acid (C6H5COOH) dissolved in 25 g of benzene shows a depression in freezing point equal to 1.62 K. Molal depression constant for benzene is 4.9 K kg mol–1. What is the percentage association of acid if it forms dimer in solution? 8) The vapour pressure of pure benzene at a certain temperature is 0.850 bar. A non-volatile, non-electrolyte solid weighing 0.5 g when added to 39.0 g of benzene (molar mass 78 g mol-1). Vapour pressure of the solution, then, is 0.845 bar. What is the molar mass of the solid substance? 9) Explain the following terms: a)Schottky defects. b) F-centre. c)Ferromangnetism d) Raoults Law e) Osmotic Pressure 10) Can you store copper sulphate solutions in a zinc pot? 11) Represent the cell in which the following reaction takes place Mg(s) + 2Ag+(0.0001M) →Mg2+(0.130M) + 2Ag(s) Calculate its E(cell) if E0cell = 3.17 V. 12) Calculate the emf of the cell in which the following reaction takes place Ni(s) + 2Ag+ (0.002 M) →Ni2+ (0.160 M) + 2Ag(s) Given that (cell) EV = 1.05 V 13) Write the Nernst equation and emf of the following cells at 298 K: (i) Mg(s)|Mg2+(0.001M)||Cu2+(0.0001 M)|Cu(s) 14) Explain Kohlrausch Law with suitable example.

15) Write cationic & anionic reactions for the following cells: a) Fuel cell b) Dry cell c) Lead storage batteries 16) For the reaction R →P, the concentration of a reactant changes from 0.03M to 0.02M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds. 17) Calculate the overall order of a reaction which has the rate expression (a) Rate = k [A] 1/2 [B] 3/2 (b) Rate = k [A] 3/2 [B] –1 18) Differentiate molecularity & order of reaction. 19) The initial concentration of N2O5 in the following first order reaction N2O5(g) →2 NO2(g) + 1/2O2 (g) was 1.24 × 10–2 mol L–1 at 318 K. The concentration of N2O5 after 60 minutes was 0.20 × 10–2 mol L–1. Calculate the rate constant of the reaction at 318 K. 20) A first order reaction is found to have a rate constant, k = 5.5 × 10-14 s-1. Find the half-life of the reaction. 21) Show that in a first order reaction, time required for completion of 99.9% is 10 times of half-life (t1/2) of the reaction. When reaction is completed 99.9%, [R]n = [R] 0 – 0.999[R]0 22) Explain pseudo first order reaction with suitable example. 23) The rate constants of a reaction at 500K and 700K are 0.02s –1 and 0.07s –1 respectively. Calculate the values of Ea and A. 24) Why is it necessary to remove CO when ammonia is obtained by Haber’s process? 25) Why is the ester hydrolysis slow in the beginning and becomes faster after sometime? 26) What is an adsorption isotherm? Describe Freundlich adsorption isotherm. 27) Why is adsorption always exothermic ? 28) Explain the following terms: (i) Electrophoresis (ii) Coagulation (iii) Hardy Schulz Rule (iv) Tyndall effect. 29) What is the role of depressant in froth floatation process? 30) Outline the principles of refining of metals by the following methods: (i) Zone refining (ii) Vapour phase refining (iii) Leaching. 31) a) What happens when PCl5 is heated? b) Why are pentahalides more covalent than trihalides ? c) Why is N2 less reactive at room temperature? d) Bond angle in PH4+ is higher than that in PH3. Why? e) What happens when white phosphorus is heated with concentrated NaOH

solution in an inert atmosphere of CO2 ? 32) a)What is the basicity of H3PO4? b) What happens when H3PO3 is heated? c)Why is H2O a liquid and H2S a gas ? d) Deduce the molecular shape of BrF3 on the basis of VSEPR theory. e) How are XeO3 and XeOF4 prepared? 33) Arrange the following in the order of property indicated for each set: (i) F2, Cl2, Br2, I2 - increasing bond dissociation enthalpy. (ii) HF, HCl, HBr, HI - increasing acid strength. (iii) NH3, PH3, AsH3, SbH3, BiH3 – increasing base strength 34) a) Why is Cr2+ reducing and Mn3+ oxidising when both have d4 configuration. b) Why is the EV value for the Mn3+/Mn2+ couple much more positive than that for Cr3+/Cr2+ or Fe3+/Fe2+? Explain. c) Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only? d) Which is a stronger reducing agent Cr2+ or Fe2+ and why ? e) Calculate the ‘spin only’ magnetic moment of M2+(aq) ion (Z = 27). 35) Actinoid contraction is greater from element to element than lanthanoid contraction. Why? 36) Indicate the steps in the preparation of: (i) K2Cr2O7 from chromite ore. (ii) KMnO4 from pyrolusite ore. 37) a) [Cr(NH3)6]3+ is paramagnetic while [Ni(CN)4]2– is diamagnetic. Explain why? b) What is meant by unidentate, didentate and ambidentate ligands? Give two examples for each. c) Write the formulas for the following coordination compounds: (i) Tetraamminediaquacobalt(III) chloride (ii) Potassium tetracyanonickelate(II) 38) Primary alkyl halide C4H9Br (a) reacted with alcoholic KOH to give compound (b). Compound (b) is reacted with HBr to give (c) which is an isomer of (a). When (a) is reacted with sodium metal it gives compound (d), C8H18 which is different from the compound formed when n-butyl bromide is reacted with sodium. Give the structural formula of (a) and write the equations for all the reactions. 39) How will you bring about the following conversions? (i) Ethane to bromoethene (ii) Propene to1-nitropropane (iii) Toluene to benzyl alcohol (iv) Propene to propyne 40)

(a) How will you bring about the following conversions? (i) Ethanal to 2- butenal (ii) Propanone to propene (b) A compound [A] with molecular formula C5H10O gave a positive 2.4 DNP test but a negative Tollen,s test. It was oxidized to carboxylic acid [B] with molecular formula C3H6O2 when treated with alkaline KMnO4 under vigorous conditions. Sodium salt of B gave a hydrocarbon [C] in Kolbe,s electrolytic reduction. Identify [A], [B] and [C] and write the chemical equations for the reactions.

OR (a) Give simple chemical test to distinguish between the following pairs of compounds. (i) Benzaldehyde and acetophenone (ii) propanal and propanone (b) Describe the following: (i) Rosenmund reaction (ii) Cannizzaro reaction (iii) Cross aldolcondensation 41)

(a) State the following; (i) Raoult,s law for liquid solutions containing non-volatile solutes. (ii) Henry,s law about partial pressure of a gas in a mixture (b) Calculate the mass of a non-volatile solute (molar mass 40 g/mol) which should be dissolved in 114 goctane to reduce its vapour pressure to 80 %. OR (a) Define term, osmotic pressure. What is the advantage of using osmotic pressure as compared to other colligative properties for the determination of molar masses of solutes in solutions? (b) What is meant by abnormal molecular mass of solute? Discuss the factors which bring abnormality in the experimentally determined molecular masses of solutes using colligative properties. 42) Describe the following reactions. a) Cannizaro's reaction b) Cross aldol condensation. c) How will you convert i) Methyl cyanide to acetamide ii) Acetaldehyde to but-2-enal iii) Ethyl benzene to benzoic acid . OR Write short notes on a) Hell– Volhard - Zelinsky reaction. b) Clemmensen reaction. c) Stephen Reaction 43) A compound A on oxidation given B (C2H4O2). ‘A’ reacts with Dil NaOH and on subsequent heating forms C. C on catalytic hydrogenation gives D. Identify A, B, C and D and write down

the reaction involved. 44) Sonya is a class XII student. Her mother fell down and bruised her leg which gave her a lot of pain. Sonya gave her mother a non narcotic analgesic which was safe to use. Her mother asked if there was some other type of analgesic as well. Sonya told her mother about narcotic analgesics and that they should be taken only with the doctor’s advice when in acute pain. Now answer the following questions:a) What values are expressed by Sonya about narcotic and non narcotic drugs? b) Give two examples of these drugs. c) Give an example of an antipyretic which also acts as an analgesic. How does it act as an analgesic ? 45) Account for the following: a) Ethyl iodide undergoes SN2 reaction faster than ethyl bromide. b) Alkyl halides though polar are insoluble in water c) Aryl halides are less reactive than alkyl halides towards nucleophilic substitution. 46) What happens when: a) N-butyl chloride is treated with alcoholic KOH? b) Methyl bromide is treated with Na in the presence of dry ether? c) Methyl chloride is treated with KCN? 47) What happens when D-glucose is treated with the following reagents? a) HI b)

Bromine water

c)

HNO3

d)

HCN

e)

NH2OH

48)

Answer the following a) What is tincture of iodine ? What is its use ? b) What are food preservatives ? c) Why is use of aspartame limited to cold foods and drinks ? d) What are artificial sweetening agents ? Give two examples e) Name the sweetening agent used in the preparation of sweets for a diabetic patient. OR a) Explain the following terms with suitable examples (i) cationic detergents (ii) anionic detergents and (iii) non-ionic detergents. b) What are biodegradable and non-biodegradable detergents ? Give one example of each. 49) Some polymers are biodegradable. But we should dispose off different polymers with care. As a student of chemistry, answer the following questions: (i)

Write two harmful effects of polymers.

(ii)

Name one aliphatic biodegradable polyester which is used in packaging and orthopaedic devices. Write its full form. (iii) Give the structures of monomers from which it is formed. Show the formation of polymer. (iv) Write the name and structure of the monomer of nylon-6. 50) a) An aromatic compound ‘A’ on treatment with aqueous ammonia and heating forms compound ‘B’ which on heating with Br2 and KOH forms a compound ‘C’ of molecular formula C6H7N. Write the structures and IUPAC names of compounds A, B and C. b) Explain the following with suitable examples: (i) Hoffman Bromamide Reaction (ii) Carbyleamine reaction (iii) Coupling Reaction